Image data is encoded by a codec in accordance with a predetermined data compression standard, for example, the Moving Picture Expert Group (MPEG) standard, and is then stored in a recording medium in the form of a bitstream or transmitted through a communication channel.
As hardware capable of reproducing and storing high-resolution or high-definition image content is being developed and supplied, there is an increasing need for a codec for effectively encoding or decoding the high-resolution or high-definition image content. The encoded image content may be decoded and then reproduced. Recently, methods of effectively compressing such high-resolution or high-definition image content have been implemented. For example, an image compression technique may be effectively implemented through a process of dividing an image to be encoded by an arbitrary method or manipulating data.
A prediction technique is the most widely used technique for encoding a video including temporally consecutive images. In the video encoding/decoding technology, the prediction technique is a technique for encoding data of a current block by using a block having information with similar tendency to the current block in the image. If the data of the current block is directly encoded, the amount of data generated by the encoding is relatively large. Therefore, only the difference information between the data of another block that has already been encoded and the data of the current block is encoded and the data generated by the encoding is transmitted or stored.
The information generated by encoding the data of the current block through the prediction technique may be defined as prediction information. At this time, information indicating another block used to encode the current block is also encoded as prediction information and then transmitted or stored.
In the prediction technique, a process of determining another block used to encode the current block is preceded. According to the prediction technique, since the current block is predicted by using information having similar tendency to the current block, neighboring samples spatially adjacent to the current block in the current image are used, or collocated blocks in spatially adjacent neighboring blocks and temporally different images are used.
According to the intra prediction technique among the prediction techniques, the sample value of the current block may be determined using neighboring sample values spatially adjacent to the current block.
According to the inter prediction technique, as another prediction technique, motion information of the current block is determined using prediction information of the adjacent block or the neighboring block such as the collocated block. The sample value of the current block may be determined using the sample value of the reference block indicated by the motion information of the current block.
The range of the information to be referred to as the prediction information of the current block in the prediction information of the adjacent block or the collocated block may be changed according to whether a mode is a skip mode, a merge mode, or an advanced motion vector prediction (AMVP) mode among the inter prediction techniques.
In particular, in the case of the skip mode or the merge mode, a merge candidate list is used to determine a neighboring block to be used for inter prediction. The motion information of the current block may be determined using one piece of motion information among at least one candidate block included in the merge candidate list.